Physics-14-EXAM IV PDF

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This is the 4th Exam practical....

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PHYSICS 14 PROF. MANCINI

FALL 2014 ________________________________ NAME

EXAM IV 1)

An electron moving in the direction of the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, the direction of the magnetic field in this region points in the direction of the A) +z-axis.

2)

D) +y-axis.

E) -y-axis.

B) 3R

C)

√3

R

D) R/

√3

E) R/9

A charged particle is moving with speed v perpendicular to a uniform magnetic field. A second identical charged particle is moving with speed 2v perpendicular to the same magnetic field. If the frequency of revolution of the first particle is f, the frequency of revolution of the second particle is A) f.

4)

C) -x-axis.

A charge is accelerated from rest through a potential difference V and then enters a uniform magnetic field oriented perpendicular to its path. The field deflects the particle into a circular arc of radius R. If the accelerating potential is tripled to 3V, what will be the radius of the circular arc? A) 9R

3)

B) -z-axis.

B) 2f.

C) 4f.

D) f/2.

E) f/4.

An electron traveling toward the north with speed 4.0 × 105 m/s enters a region where the Earth's magnetic field has the magnitude 5.0 × 10-5 T and is directed downward at 45° below horizontal. What is the magnitude of the force that the Earth's magnetic field exerts on the electron? (e = 1.60 × 10-19 C) A) 2.3 × 10-18 N D) 3.2 × 10-19 N

B) 3.2 × 10-18 N E) 2.3 × 10-20 N

C) 2.3 × 10-19 N

5)

A uniform magnetic field of magnitude 0.80 T in the negative z direction is present in a region of space, as shown in the figure. A uniform electric field is also present and is set at 76,000 V/m in the +y direction. An electron is projected with an initial velocity v0 = 9.5 × 104 m/s in the +x direction. The y component of the initial force on the electron is closest to which of the following quantities? (e = 1.60 × 10-19 C)

A) -2.4 × 10-14 N D) +1.0 × 10-14 N

6)

B) +2.4 × 10-14 N

C) -1.0 × 10-14 N

E) zero

An electron moving with a velocity = 5.0 × 107 m/s î enters a region of space where perpendicular electric and a magnetic fields are present. The electric field is = ĵ. What magnetic field will allow the electron to go through the region without being deflected? A)

= +2.0 × 10-4 T ĵ

B)

= -2.0 × 10-4 T ĵ

D)

= -2.0 × 10-4 T

E)

= +5.0 × 10-4 T

C)

= +2.0 × 10-4 T

7)

The figure shows a velocity selector that can be used to measure the speed of a charged particle. A beam of particles is directed along the axis of the instrument. A parallel plate capacitor sets up an electric field E, which is oriented perpendicular to a uniform magnetic field B. If the plates are separated by 2.0 mm and the value of the magnetic field is 0.60 T, what voltage between the plates will allow particles of speed 5.0 × 105 m/s to pass straight through without deflection?

A) 600 V

8)

D) 190 V

E) 94 V

B) 30°

C) 35°

D) 60°

E) 90°

A conducting bar slides without friction on two parallel horizontal rails that are 50 cm apart and connected by a wire at one end. The resistance of the bar and the rails is constant and equal to 0.10 Ω. A uniform magnetic field is perpendicular to the plane of the rails. A 0.080-N force parallel to the rails is required to keep the bar moving at a constant speed of 0.50 m/s. What is the magnitude of the magnetic field? A) 0.10 T

10)

C) 3800 V

A straight wire that is 0.60 m long is carrying a current of 2.0 A. It is placed in a uniform magnetic field of strength 0.30 T. If the wire experiences a force of 0.18 N, what angle does the wire make with respect to the magnetic field? A) 25°

9)

B) 1900 V

B) 0.25 T

C) 0.36 T

D) 0.54 T

E) 0.93 T

A thin copper rod that is 1.0 m long and has a mass of 0.050 kg is in a magnetic field of 0.10 T. What minimum current in the rod is needed in order for the magnetic force to cancel the weight of the rod? A) 1.2 A

B) 2.5 A

C) 4.9 A

D) 7.6 A

E) 9.8 A

11)

An L-shaped metal machine part is made of two equal-length segments that are perpendicular to each other and carry a 4.50-A current as shown in the figure. This part has a total mass of 3.80 kg and a total length of 3.00 m, and it is in an external 1.20-T magnetic field that is oriented perpendicular to the plane of the part, as shown. What is the magnitude of the NET magnetic force that the field exerts on the part?

A) 8.10 N

12)

B) 11.5 N

C) 16.2 N

D) 22.9 N

E) 32.4 N

A wire segment 1.2 m long carries a current I = 3.5 A and is oriented as shown in the figure. A uniform magnetic field of magnitude 0.50 T pointing toward the -x direction is present as shown. The +z-axis points directly into the page. What is the magnetic force vector on the wire segment?

A) +1.6 N ĵ

C) +1.6 N

B) -1.6 N

D) (+1.3 ĵ - 1.6 ) N E) (-1.3 ĵ + 1.6

N

13)

Suppose that you wish to construct a simple ac generator having an output of 12 V maximum when rotated at 60 Hz. A uniform magnetic field of 0.050 T is available. If the area of the rotating coil is 100 cm2, how many turns do you nee A) 8

14)

C) 32

D) 64

E) 128

You are designing a generator to have a maximum emf of 8.0 V. If the generator coil has 200 turns and a cross-sectional area of 0.030 m2, what should be the frequency of the generator in a uniform magnetic field of 0.030 T? A) 7.1 Hz

15)

B) 16

B) 7.5 Hz

C) 8.0 Hz

D) 22 Hz

E) 44 Hz

Wire is wound on a square frame, 30 cm by 30 cm, to form a coil of 7 turns. The frame is mounted on a horizontal shaft through its center (perpendicular to the plane of the diagram), as shown in the figure. The coil is in clockwise rotation, with a period of 0.060 s. A uniform, horizontal, magnetic field of magnitude 0.40 T is present. At a given instant, the plane of the coil forms a 60° angle with the horizontal, as shown. At that instant, what is the magnitude of the emf induced in the coil?

A) 26 V

B) 23 V

C) 2.1 V

D) 3.6 V

E) 13 V

16)

As shown in the figure, a wire and a 10-Ω resistor are used to form a circuit in the shape of a square, 20 cm by 20 cm. A uniform but nonsteady magnetic field is directed into the plane of the circuit. The magnitude of the magnetic field is decreased from 1.50 T to 0.50 T in a time interval of 63 ms. The average induced current and its direction through the resistor, in this time interval, are closest to

A) 63 mA, from b to a. D) 38 mA, from a to b.

17)

B) 38 mA, from b to a. E) 95 mA, from a to b.

C) 63 mA, from a to b.

Three very long, straight, parallel wires each carry currents of 4.00 A, directed out of the page as shown in the figure. The wires pass through the vertices of a right isosceles triangle of side 2.00 cm. What is the magnitude of the magnetic field at point P at the midpoint of the hypotenuse of the triangle?

A) 4.42 × 10-6 T D) 1.26 × 10-4 T

B) 1.77 × 10-5 T E) 1.77 × 10-6 T

C) 5.66 × 10-5 T

18)

A very long straight wire carries a 12-A current eastward and a second very long straight wire carries a 14-A current westward. The wires are parallel to each other and are 42 cm apart. Calculate the force on a 6.4 m length of one of the wires. (μ0 = 4π × 10-7 T ∙ m/A) A) 8.0 × 10-7 N D) 5.1 × 10-6 N

19)

B) 7.8 × 10-7 N E) 49.8 × 10-6 N

C) 9.8 × 10-8 N

A circular loop of wire of radius 10 cm carries a current of 6.0 A. What is the magnitude of the magnetic field at the center of the loop? (μ0 = 4π × 10-7 T ∙ m/A) A) 3.8 × 10-5 T D) 1.2 × 10-7 T

21)

C) 8.0 × 10-5 N

A rectangular loop of wire measures 1.0 m by 1.0 cm. If a 7.0-A current flows through the wire, what is the magnitude of the magnetic force on the centermost 1.0-cm segment of the 1.0-m side of the loop? (μ0 = 4π × 10-7 T ∙ m/A) A) 3.2 × 10-6 N D) 4.9 × 10-6 N

20)

B) 5.1 × 10-4 N E) 2.2 × 10-4 N

B) 3.8 × 10-7 T E) 3.8 × 10-8 T

C) 1.2 × 10-5 T

Two coaxial circular coils of radius R = 15 cm, each carrying 4.0 A in the same direction, are positioned a distance d = 20 cm apart, as shown in the figure. Calculate the magnitude of the magnetic field halfway between the coils along the line connecting their centers. (μ0 = 4π × 10-7 T ∙ m/A)

A) 0.90 × 10-5 T

B) 3.9 × 10-5 T

C) 1.9 × 10-5 T

D) 6.3 × 10-5 T

22)

E) 9.2 × 10-5 T

A long straight very thin wire on the y-axis carries a 10-A current in the positive y-direction. A circular loop 0.50 m in radius, also of very thin wire and lying in the yz-plane, carries a 9.0-A current, as shown. Point P is on the positive x-axis, at a distance of 0.50 m from the center of the loop. What is the magnetic field vector at point P due to these two currents? (μ0 = 4π × 10-7 T ∙ m/A)

A) zero

B) -8.0 × 10-6 T

D) (-4.0 × 10-6 T) î - (4.0 × 10-6 T) 23)

C) (+4.0 × 10-6 T) î - (4.0 × 10-6 T) E) (-4.0 × 10-6 T) î - (8.0 × 10-6 T)

A coil lies flat on a tabletop in a region where the magnetic field vector points straight up. The magnetic field vanishes suddenly. When viewed from above, what is the direction of the induced current in this coil as the field fades? A) counter-clockwise then clockwise C) clockwise E) There is no current induced in the coil.

24)

B) clockwise then counter-clockwise D) counter-clockwise

A 2.0-m long conducting wire is formed into a square and placed in the horizontal A uniform magnetic field is oriented 30.0° above the horizontal with a strength of 9.0 T. What is the magnetic flux through the square? A) 1.1 T ∙ m2 D) 18 T ∙ m2

25)

B) 1.9 T ∙ m2 E) 43 T ∙ m2

C) 2.3 T ∙ m2

A circular coil of radius 5.0 cm and resistance 0.20 Ω is placed in a uniform magnetic field perpendicular to the plane of the coil. The magnitude of the field changes with time according to B = 0.50e-20t T. What is the magnitude of the

current induced in the coil at the time t = 2.0 s? A) 1.3 mA

B) 9.2 mA

C) 7.5 mA

D) 4.2 mA

E) 2.6 mA...